Mass plate electrodes for button cells are presently manufactured by placing a tablet formed of pressed active material powder in a cup of nickel gauze, placing a lid of nickel gauze within the cup, over the tablet, and then folding over the upper peripheral edge portion of the cup inwardly through 90.degree. towards the cup centre to retain the peripheral portion of the lid between the closure portion of the cup thus formed and the tablet of active material. The assembly is then pressed between a punch and die to obtain the final size and shape of the electrode.
Thus, according to conventional practice, a mass plate electrode, for a button cell, comprises a mass of active material having first and second main surfaces and a side surface interconnecting the first and second main surfaces; a cup of liquid-permeable metal sheet having a base portion adjacent the first main surface of the mass, a side wall portion adjacent the side surface of the mass, and a peripheral closure portion; and a lid having an inner portion adjacent the second main surface of the mass, and a peripheral closure portion held by the peripheral closure portion of the cup.
One disadvantage of this known electrode construction is that due to the necessity of placing the tablet of active material and the lid inside the cup, this method of manufacture is difficult to automate. Moreover, when the cup and the lid are formed from metal gauze or mesh, it is difficult to carry out punching of the gauze or mesh without the formation of strands or whiskers which protrude from the cut edges and, at a later stage in the manufacture of the botton cell, these whiskers can cause short circuits with other electrodes of the cell.